Problem: Graph this system of equations and solve. $3x-3y = -9$ $2x+3y = -6$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$ $\llap{-}2$ $\llap{-}3$ $\llap{-}4$ $\llap{-}5$ $\llap{-}6$ $\llap{-}7$ $\llap{-}8$ $\llap{-}9$ $\llap{-}10$ $1$ $2$ $3$ $4$ $5$ $6$ $7$ $8$ $9$ $10$ $\llap{-}2$ $\llap{-}3$ $\llap{-}4$ $\llap{-}5$ $\llap{-}6$ $\llap{-}7$ $\llap{-}8$ $\llap{-}9$ $\llap{-}10$ Click and drag the points to move the lines.
Explanation: Convert the first equation, $3x-3y = -9$ , to slope-intercept form. $y = x + 3$ The y-intercept for the first equation is $3$ , so the first line must pass through the point $(0, 3)$ The slope for the first equation is $1$ . Remember that the slope tells you rise over run. So in this case for every $1$ position you move up You must also move $1$ position to the right. $1$ position to the right. $1$ position up from $(0, 3)$ is $(1, 4)$ Graph the blue line so it passes through $(0, 3)$ and $(1, 4)$ Convert the second equation, $2x+3y = -6$ , to slope-intercept form. $y = -\dfrac{2}{3} x - 2$ The y-intercept for the second equation is $-2$ , so the second line must pass through the point $(0, -2)$ The slope for the second equation is $-\dfrac{2}{3}$ . Remember that the slope tells you rise over run. So in this case for every $2$ positions you move down (because it's negative) $3$ positions to the right. $2$ positions down from $(0, -2)$ is $(3, -4)$ Graph the green line so it passes through $(0, -2)$ and $(3, -4)$ The solution is the point where the two lines intersect. The lines intersect at $(-3, 0)$.